We apply for a shared instrument grant to purchase a Bruker EMX series electron paramagnetic resonance (EPR) spectrometer to be used for biochemical and medical research. This system will be used to gradually phase out the aged Varian E-6 machine at Rice University, Biochemistry and Cell Biology. Demand for this spectrometer is justified at multiple levels: * A steady increase in usage of EPR technologies in biochemical and biophysical studies at the University of Texas Medical School at Houston and at Rice University. To guarantee a reliable EPR facility for ongoing research and training purposes, we chose to buy the Bruker EMX EPR spectrometer for its durability and use of use. * EPR is a powerful tool in the structural analysis of the many biological systems that involve organic radicals and transition metal centers. This EPR capability will integrate with the Structural Biology Center at the UT-Houston Medical School to complement the existing nuclear magnetic resonance (NMR) facility and with the Center's imminent recruitment of a X-ray crystallographer. * The quested EPR system will continue and expand service to a wide spectrum of users joining the Houston Area Molecular Biophysical Training Program, thus strengthening the scientific interactions among scientists at UT Medical School, Rice University, Baylor College of Medicine and University of Houston.